An afocal freeform telescope has been prototyped at MIT Lincoln Laboratory. The design leverages an upgraded version of the Laboratory’s FANO design code to produce designs in afocal-space rather than imaging-space. The FANO code is unique, as it optimizes the surfaces using a Non-Uniform Rational B-Spline (NURBS) description rather than a polynomial-based equation. This approach allows the mirrors to take the most optimal shape without the limit of number of polynomial terms often hard-coded into commercial design software. Design comparisons with polynomial-based approaches are discussed showing improved performance when designing with NURBS shapes. Test results from the 150-mm diameter, 6x afocal magnification, 4° field-of-view prototype unit operating in the near-infrared band are shown.
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